Vivariums house a number of animals, typically test animals, such as mice, in a number of cages, often a large number. The test animals are frequently used test drugs, genetics, animal strains, husbandry experiments, methods of treatment, procedures, diagnostics, and the like. We refer to all such uses of a vivarium as a study.
Regular weighing of animals is an important part of studies. In the prior art, weighing was labor intensive and often the handling of the animals changed their behavior or their health, changing the results or quality if the study. Handling of animals by humans to weight them comprised the sterility of the cages and animals, and put the health of the animals and workers at risk.
Such manual weight recording is inherently infrequent due to the high labor time and cost. This infrequency creates three weakness of the prior art. First, problems may not be discovered until after an unacceptable delay, such as failure to eat. Second, subtle behavior or health attributes, such as an animal's eating schedule, will be missed. Third, manual observation requires light for the observer. For many animals, the light interferes with and alters their behavior and health, and thus alters the results of the study compared with animals in their natural lighting regimen.
Vivarium cages are normally pathogen-free. Animals and thus their cages must be isolated from outside pathogens or contamination and from pathogens or contamination from other animals or other cages. This presents a significant challenge to vivarium automation and in particular to in-cage animal weighing and automatic animal identification. Electronic equipment placed inside a cage may need to be discarded after a single study due to the inability to sterilize the equipment between studies. Such equipment may be an animal ID sensor, a scale, or a wireless transmitter. In addition, in order to keep the cages pathogen-free it is desirable to have as few cage penetrations as possible. This means that power or data wiring to electronic equipment inside the cage is undesirable. Although this requirement motivates wireless devices, these devices must then be battery powered, which adds to cost, size and weight, and may introduce pathogens. Batteries may have to be changed out during a study, which adds to both equipment and labor costs, and may introduce pathogens.
Sterility or pathogen free is important in vivariums to assure the health of the animals and the health of the workers. Also, sterility is critical for accurate, consistent, credible and repeatable study results. Sterility refers to the sufficient restriction of pathogens so as to not so affect the outcome of the study or health or behavior of animals or people. Sterility also refers to husbandry attributes, supplies and usage, as well as health.